Hoping to spot travelers with fevers, a Japanese quarantine officer uses a heat-sensitive camera to monitor arrivals at Narita International Airport on April 26, 2009.

In the U.S., border officers wearing protective gear, such as gloves and masks, have begun "passive screening" of travelers entering the country, mainly by "asking people about fever and illness, looking for people who are ill," Centers for Disease Control and Prevention acting director Richard Besser told the Associated Press.